In recent years, adding newly the anisotropic properties or improving markedly the properties for ceramics have been examined by crystal orientation.
As a process for fabrication of crystal oriented ceramics, for example, the following process has been known. A strong magnetic field of 1 tesla (T) or greater and preferably 3 tesla (T) or greater is applied to an α-type alumina slurry prepared by mixing α-type alumina particles and a solvent, and axis of easy magnetization of the α-type alumina particles are oriented parallel direction to an applied magnetic field. An axis of easy magnetization indicates a crystal axis having a small diamagnetic susceptibility and an axis of easy magnetization of α-type alumina indicates a c-axis. Thereafter, an α-type alumina green compact consisted of α-type alumina particles which the c-axis is oriented parallel direction to an applied magnetic field is prepared, and the α-type alumina green compact is sintered. In this manner, the c-axis oriented alumina ceramics consisted of the α-type alumina grains which the c-axis is oriented parallel direction to the magnetic field is prepared. According to this process, the c-axis oriented alumina ceramics having an arbitrary shape which is fabricated by orientation of the α-type alumina particles can be easily produced.
In such an orientation method using a magnetic field, anisotropy of magnetization energy generated in material (particles) by applying a magnetic field becomes a driving force of orientation and the particles can be in a case where the anisotropy of magnetic energy is greater than thermal vibration energy. Since the magnetization energy is proportional to the volume of particles, the particles are easily when the size of the particles is large.